A water filter removes impurities from water by using, e.g., a fine physical barrier, a physical process, a chemical process or a biological process. Filters cleanse water to various extents for numerous applications including irrigation, drinking water, aquariums, and swimming pools. Point-of-use filters for home use mostly include granular-activated carbon filters (GAC), powdered-activated carbon (PAC), metallic alloy filters, microporous ceramic filters, ion exchange resins, carbon block resin (CBR) and ultrafiltration membranes.
Water filters may be incorporated in various types of devices including water or other drink dispensers. These dispensers may be stand alone units, or may be integrated into other appliances, such as a refrigerator. Typically, filters are used up over time, and must be replaced periodically. In some cases, the manufacturer of the dispenser may wish to provide proprietary replacement filters matched to a given dispenser type, and to prevent the use of unauthorized filters.